This invention relates to a method for reducing contamination of a corona charger in an electrophotographic process by identifying and directing contaminated airflow streams away from the corona charger.
In many electrophotographic processes for the production of copies, corona charges are used to impart a charge to a photoconductive film which is subsequently passed to an imaging section, a developing section and an image transfer section where the image on the photoconductor film is transferred to a paper to produce a copy of the image on the paper. The paper is subsequently passed to a fuser section where a toner image on the paper is fixed to the paper by elevated temperature and pressure in the fuser section. The photoconductor film then passes through a neutralization section and thereafter past a brush cleaner which removes contaminants from the film prior to passing the photoconductor film back to the primary charging section.
Many of the operations conducted in the photocopying process generate contaminated air streams which may be directed to and passed by or into the corona charger. Such streams are typically produced in copier machine systems such as the environmental control system, the cleaning blower system, the writer blower system, paper transport fan systems, cooler fan systems, the charger rest blower system and the like. All of these systems produce air streams which may contain contaminants of one sort or another. Particularly, streams which may contain fuser oil or toner represent significant contaminants to the corona charger.
As well known to those skilled in the art, as shown for instance in U.S. Pat. No. 5,424,540, xe2x80x9cCorona Charger Wire Tensioning Mechanismxe2x80x9d issued Jun. 13, 1995 to Garcia, et al and U.S. Pat. No. 6,038,120, xe2x80x9cAC Corona Charger With Buried Floor Electrodexe2x80x9d issued Mar. 14, 2000 to May, et al., it is disclosed that corona chargers typically include bare corona wires which are located between a grid electrode and a shield. These patents are hereby incorporated by reference. These wires are relatively small in diameter and since they are highly charged, contamination of these wires by materials such as fuser oil, toner dust particles and the like can create charger arcing which causes machine errors and non-uniform charging which creates copy image problems.
One approach to the control of such contamination is the control of the flow of such contamination from the sources of the contamination. This requires very close control of the environment around substantially every operating system in the copy machine and is not considered feasible.
Nevertheless, it is necessary that the corona charger be replaced relatively frequently or that a system be developed to minimize contamination of the corona charger by airborne contaminants in the copy machine.
Accordingly, a continuing search has been directed to the development of methods to minimize such contamination.
According to the present invention, contamination of a corona charger is reduced in an electrophotographic process wherein the corona charger imparts a charge to a photoconductor film passed by the corona charger by: identifying contaminated air flow streams and determining the direction of flow of the contaminated air flow stream flowing past or into the corona charger and positioning at least one plate to divert the contaminated air flow streams away from the corona charger.
The invention further comprises a contamination protected corona charger system comprising: a corona charger; at least one plate positioned to direct contaminated air flows away from the corona charger and at least partially enclose a controlled air circulation space around the corona charger and a clean gas supply positioned to discharge a clean gas between the at least one plate and a photoconductor film passed by the corona charger to provide a positive clean gas pressure between the at least one plate and the photoconductor film in the controlled air circulation space.
The invention also comprises an improvement in a method for producing photocopies wherein a corona charger is used to charge a photoconductor film passed by the corona charger, the improvement comprising identifying and determining the flow direction of contaminated air flow streams and positioning at least one plate to divert the contaminated air flow streams away from the corona charger.